Material deposition and other substrate processing are widely used in window glass coating, flat panel display manufacturing, coating on flexible films (such as webs), hard disk coating, industrial surface coating, semiconductor wafer processing, photovoltaic panels, and other applications. Materials are sputtered off a target or vaporized from a source and deposited on a substrate. Materials can also be deposited by chemical vapor deposition method. A deposition process may include the following steps: a substrate can be placed in the process chamber. The chamber is evacuated and back filled with a desirable gas. The deposition is carried out. The process chamber can be vented before the substrate is taken out. The evacuation of the process chamber can take much time and limit the throughput of the deposition system. In addition, residues of the atmosphere or reaction with atmosphere can also affect the quality of deposited material.
To address the issues of throughput and environment control, one can employ a load lock in connection with a processing chamber. A substrate can be loaded in the load lock in an atmospheric environment. The load lock is then evacuated to vacuum or to reach conditions similar to the process chamber. The substrate is then transported by a transport mechanism into the process chamber to conduct processing steps such as cleaning, etching, and deposition. The substrate is then removed from the process chamber to the load lock. Commercial vacuum processing equipment can include the following types: single load lock and single process chamber, in-line system with one load lock at each end of the system, cluster tool with one or more central substrate transfer modules. The single load lock and single process chamber system requires an active transportation mechanism to carry entire substrate over a long distance without mechanical support and can not carry heavy substrate. In addition, most single load lock and single process chamber system can only load one substrate at a time and have limited throughput. The in-line system requires two load locks and an active transport system either inside vacuum or through the vacuum envelope. The cluster tool requires one or more large central transfer modules to actively transport the work pieces. When several process chambers are present, the transport mechanism is required to move the work pieces between various process stations. The transport mechanism is required not to introduce gas or air to the vacuum or controlled environment. The transport mechanism can use low power and low out-gassing vacuum motors, or use bellows or seals to transfer motion from outside the vacuum. The typical moving mechanism carries the entire substrate and typically requires heavy and expensive mechanism. The seals or bellows have limited lifetime and are also expensive. The active motors require constant monitoring and are a major cause of failures. The complexity of the aforementioned active transport mechanisms increases the system cost and reduces reliability.
Therefore there is a need for a simple and reliable system for deposition or other vacuum processing operations having desired throughput and deposition quality.